Phenols are readily alkylated by reaction of phenol with olefin in contact with an acidic catalyst. This produces a mixture of mono, di and tri-alkylphenols and all positional isomers, mainly 2-alkyl, 4-alkyl, 2,4-dialkyl and 2,4,6-trialkyl. Ecke et al. U.S. Pat. No. 2,831,898 describe a method of selectively orthoalkylating phenol by reaction with an olefin using an aluminum phenoxide catalyst. The product is mainly 2,6-dialkylphenol containing minor amounts of 2-alkylphenol.
Hahn U.S. Pat. No. 3,290,389 describes a process for alkylating phenol with olefins under pressure using a gamma alumina catalyst at 200-400.degree. C. With propylene and butene, the products were mainly 2-alkyl and 2,6-dialkylphenol.
Napolitano U.S. Pat. No. 3,367,981 is similar to Hahn but expands the useful catalyst to include all transitional aluminas.
Sparks U.S. Pat. No. 3,670,030 describes an improvement in the gamma alumina catalyzed ortho-alkylation of phenol with olefins in which catalyst life is prolonged by adding a controlled amount of water to the phenol. A preferred water content is 1000-3000 ppm.
Tamura et al. U.S. Pat. No. 4,599,465 teach that catalytic activity of gamma alumina can be increased by reducing the water content of the phenol below 250 ppm. This requires the additional step of removing water from commercially available phenol by methods such as distillation, blowing inert gas through the heated phenol, absorbing water with a desiccant such as a molecular sieve, zeolite, alumina or ion exchange resin. The test data reports time required to reach a 70% conversion of in a batch operation which was less with dried phenol than with wet phenol.
A need exists for a process of ortho-alkylating phenol with olefin using an activated alumina catalyst that will give both the high catalytic activity and selectivity sought by Tamura et al. and a prolonged catalyst life sought by Sparks.